Steve, that's why I asked for info on the pump as there are HP pumps out there but most times builders install an HV pump since by pumping more oil a HV pump ends up giving you more pressure (over a standard pump) across all running conditions as long as the down stream passages (resistance to flow) haven't changed. Changes such as enlarging of oil passages.
Kevin, I'm with the guys thinking that there is something wrong and that a complete bearing inspection is in order.
I'm running a Melling HV pump in my 383 and even though I had a baffled pan and 5 liters of oil I was getting a drop of pressure on acceleration also. I nailed it down to the Mopar windage tray, the return slots were to small and not enough of them and the oil was running out the back of the tray instead of going straight down. I switched to a Milodon pan which has more slots and they're larger and problem gone. My cold idle is 80psi and hot idle 50psi running 10W30.
I've also got a spare 187 dimpled pan that I'm going to have my welder add 2" to the sump and install it this winter and no I won't forget the pickup